In recent years, user terminals such as portable telephone terminals capable of performing communication have come into wide use. For example, portable telephone terminals can perform calling, transmission and reception of electronic mail, transmission and reception of instant messages, and the like using identification information such as telephone numbers or mail addresses fixedly given from telecommunication carriers, service providers, or the like.
Further, technologies for using other telephone numbers in one portable telephone terminal in addition to the telephone numbers fixedly given from the telecommunication carriers are known. By using such technologies, it is possible to switch telephone numbers according to the positions of portable telephone terminals or switch telephone numbers according to uses of the users of the portable telephone terminals.
As a technology for switching telephone numbers in the related art, WO 2009/013808 discloses a technology for switching telephone numbers. WO 2009/013808 discloses the technology for acquiring machine numbers of the portable telephone terminals and additional telephone numbers in advance corresponding to IDs acquired from IC tags present within specific areas when portable telephone terminals transmit requests including the machine numbers of the portable telephone terminals and the IDs.